Centos, Fedora, Debian or Mandriva

I use the One hundreds two years ago in my small company, up-to-date for the version 5.6 with assist it of the tutorial The Perfect Server - CentOS 5.6 x86_64 [ISPConfig 3].

I have two servers: One to e-mail and another to put up the company sites.

Use in the e-mail server the Virtual tutorial Users And Domains With Postfix, Courier, MySQL And SquirrelMail (CentOS 5.3 x86_64) with some updates done by my account and risk.

I have difficulties updating the packages included in the Virtual tutorial Users And Domains...

On the other hand, the Virtual tutorial Users And Domains With Postfix, Courier, MySQL And SquirrelMail (CentOS 5.3 x86_64) was published in 12-05-2009 and did not have anymore no update after this date.

I suffered a racker attack's and lost my email server'S. Am fighting to 4 days to put the server in condition to use again.

Now, in view of the difficulties updating the Virtual tutorial Users And Domains With Postfix, Courier, MySQL And SquirrelMail (CentOS 5.3 x86_64) have to do a downgrade if it wants to have my server again. That is to retroact technologically.

I thus ask to to this community:
1. Should change the CentOS for other distribution (Fedora, Debian, Mandriva, etc...)?
2. Which of them would it be more advisable and what owns a faster update?

Both links to do Debian's Download are not answering: <Http://cdimage.debian.org/debian-cd/6.0.0/i386/iso0.0-i386-netinst.iso> (i386) or <http://cdimage.debian.org/debian-cd/6.0.0/amd64/iso0.0-amd64-netinst.iso> (x86_64).